Welcome to theRECIST 1.1Quick Reference

*Eisenhauer, E. A., et al.New responseevaluation criteria insolid tumours: RevisedRECIST guideline(version 1.1). Eur JCancer 2009;45:228-47.

Subject Eligibility

Only patients with measurable disease at baseline

should be included in protocols where objective

tumor response is the primary endpoint. Measurable

disease is defined as the presence of at least one

measurable lesion.

In studies where the primary endpoint is tumor

progression (either time to progression or proportion

with progression at a fixed date), the protocol must

specify if entry is restricted to those with measurable

disease or whether patients having non-measurable

disease only are also eligible.

Methods of Assessment

The same method of assessment and the same tech -

nique should be used to characterize each identified

and reported lesion at baseline and during follow-up.

• CT is the best currently available and reproducible

method to measure lesions selected for response

assessment. MRI is also acceptable in certain

situations (e.g., for body scans but not for lung).

• Lesions on a chest X-ray may be considered

measurable lesions if they are clearly defined

and surrounded by aerated lung. However, CT is

preferable.

• Clinical lesions will only be considered measurable

when they are superficial and ≥10 mm in

diameter as assessed using calipers. For the

case of skin lesions, documentation by color

photography, including a ruler to estimate the

size of the lesion, is recommended.

• Ultrasound (US) should not be used to measure

tumor lesions.

Methods of Assessment (continued)

• Tumor markers alone cannot be used to assess

response. If markers are initially above the upper

normal limit, they must normalize for a patient to

be considered in complete response.

• Cytology and histology can be used in rare

cases (e.g., for evaluation of residual masses

to differentiate between Partial Response and

Complete Response or evaluation of new or

enlarging effusions to differentiate between

Progressive Disease and Response/Stable

Disease).

• Use of endoscopy and laparoscopy is not advised.

However, they can be used to confirm complete

pathological response.

Baseline Disease Assessment

All baseline evaluations should be performed as

closely as possible to the beginning of treatment and

never more than 4 weeks before the beginning of

the treatment.

Measurable lesionsMust be accurately measured in at least one

dimension (longest diameter in the plane of

measurement is to be recorded) with a minimum

size of:

• 10 mm by CT scan (CT scan slice thickness no

greater than 5 mm; when CT scans have slice

thickness >5 mm, the minimum size should be

twice the slice thickness).

• 10 mm caliper measurement by clinical exam

(lesions which cannot be accurately measured

with calipers should be recorded as non-

measurable).

• 20 mm by chest X-ray.

Baseline Disease Assessment

Measurable lesions (continued)

• Malignant lymph nodes To be considered pathologically enlarged and

measurable, a lymph node must be ≥15 mm in

short axis when assessed by CT scan (CT scan

slice thickness is recommended to be no greater

than 5 mm). At baseline and in follow-up, only the

short axis will be measured and followed.

• Lytic bone lesions or mixed lytic-blasticlesions with identifiable soft tissue components

that can be evaluated by cross-sectional imaging

techniques such as CT or MRI can be considered

measurable if the soft tissue component meets the

definition of measurability described above.

• ‘Cystic lesions’ thought to represent cystic

metastases can be considered measurable if they

meet the definition of measurability described

above. However, if non-cystic lesions are present

in the same patient, these are preferred for

selection as target lesions.

Baseline Disease Assessment

Non-measurable lesionsNon-measurable lesions are all other lesions,

including small lesions (longest diameter <10 mm

or pathological lymph nodes with 10 to <15 mm

short axis), as well as truly non-measurable lesions.

Lesions considered truly non-measurable include:

leptomeningeal disease, ascites, pleural or

pericardial effusion, inflammatory breast disease,

lymphangitic involvement of skin or lung, abdominal

masses/abdominal organomegaly identified by

physical exam that is not measurable by

reproducible imaging techniques.

• Blastic bone lesions are non-measurable.

• Lesions with prior local treatment, such as

those situated in a previously irradiated area or in

an area subjected to other loco-regional therapy,

are usually not considered measurable unless

there has been demonstrated progression in the

lesion. Study protocols should detail the conditions

under which such lesions would be considered

measurable.

Target Lesions

• All measurable lesions up to a maximum of two

lesions per organ and five lesions in total,

representative of all involved organs, should be

identified as target lesions and recorded and

measured at baseline.

• Target lesions should be selected on the basis of

their size (lesions with the longest diameter) and

be representative of all involved organs, as well as

their suitability for reproducible repeated

measurements.

• All measurements should be recorded in metric

notation using calipers if clinically assessed.

A sum of the diameters (longest for non-nodal

lesions, short axis for nodal lesions) for all targetlesions will be calculated and reported as the

baseline sum diameters, which will be used as

reference to further characterize any objective tumor

regression in the measurable dimension of the

disease. If lymph nodes are to be included in the

sum, only the short axis will contribute.

Non-target Lesions

All lesions (or sites of disease) not identified as

target lesions, including pathological lymph nodes

and all non-measurable lesions, should be identified

as non-target lesions and be recorded at baseline.

Measurements of these lesions are not required and

they should be followed as ‘present’, ‘absent’ or in

rare cases, ‘unequivocal progression’.

Response Criteria

Evaluation of target lesionsComplete Response (CR):

Disappearance of all target lesions. Any pathological

lymph nodes (whether target or non-target) must

have reduction in short axis to <10 mm.

Partial Response (PR):

At least a 30% decrease in the sum of diameters of

target lesions, taking as reference the baseline sum

of diameters.

Progressive Disease (PD):

At least a 20% increase in the sum of diameters of

target lesions, taking as reference the smallest sum

on study (this may include the baseline sum). The

sum must also demonstrate an absolute increase of

at least 5 mm.

Stable Disease (SD):

Neither sufficient shrinkage to qualify for PR nor

sufficient increase to qualify for PD.

Response Criteria

Special notes on the assessment of target lesions

• Lymph nodes identified as target lesions should

always have the actual short axis measurement

recorded even if the nodes regress to below 10 mm

on study. When lymph nodes are included as

target lesions, the ‘sum’ of lesions may not be

zero even if complete response criteria are met

since a normal lymph node is defined as having a

short axis of <10 mm.

• Target lesions that become ‘too small tomeasure’. While on study, all lesions (nodal and

non-nodal) recorded at baseline should have their

actual measurements recorded at each

subsequent evaluation, even when very small.

However, sometimes lesions or lymph nodes

become so faint on a CT scan that the radiologist

may not feel comfortable assigning an exact

measure and may report them as being ‘too small

to measure’, in which case a default value of 5 mm

should be assigned.

Response Criteria

Special notes on the assessment of target lesions (continued)

• Lesions that split or coalesce on treatment.When non-nodal lesions ‘fragment’, the longest

diameters of the fragmented portions should be

added together to calculate the target lesion sum.

Similarly, as lesions coalesce, a plane between

them may be maintained that would aid in

obtaining maximal diameter measurements of

each individual lesion. If the lesions have truly

coalesced such that they are no longer separable,

the vector of the longest diameter in this instance

should be the maximal longest diameter for the

‘coalesced lesion’.

Response Criteria

Evaluation of non-target lesionsComplete Response (CR):

Disappearance of all non-target lesions and normal -

ization of tumor marker levels. All lymph nodes must

be non-pathological in size (<10 mm short axis).

Non-CR / Non-PD:

Persistence of one or more non-target lesion(s)

and/or maintenance of tumor marker levels above

normal limits.

Progressive Disease (PD):

Unequivocal progression of existing non-target lesions.

• When patient has measurable disease. To

achieve ‘unequivocal progression’ on the basis of

the non-target disease, there must be an overall

level of substantial worsening in non-target

disease such that, even in presence of SD or PR

in target disease, the overall tumor burden has

increased sufficiently to merit discontinuation of

therapy. A modest ‘increase’ in the size of one or

more non-target lesions is usually not sufficient

to qualify for unequivocal progression status.

Response Criteria

Progressive Disease (PD):

Unequivocal progression of existing non-target lesions

(continued)

• When patient has only non-measurabledisease. There is no measurable disease

assessment to factor into the interpretation of

an increase in non-measurable disease burden.

Because worsening in non-target disease cannot

be easily quantified, a useful test that can be

applied is to consider if the increase in overall

disease burden based on change in non-

measurable disease is comparable in magnitude

to the increase that would be required to declare

PD for measurable disease. Examples include an

increase in a pleural effusion from ‘trace’ to ‘large’

or an increase in lymphangitic disease from

localized to widespread.

Response Criteria

New lesionsThe appearance of new malignant lesions denotes

disease progression:

• The finding of a new lesion should be unequivocal

(i.e., not attributable to differences in scanning

technique, change in imaging modality or findings

thought to represent something other than tumor,

especially when the patient’s baseline lesions

show partial or complete response).

• If a new lesion is equivocal, for example because

of its small size, continued therapy and follow-up

evaluation will clarify if it represents truly new

disease. If repeat scans confirm there is definitely

a new lesion, then progression should be declared

using the date of the initial scan.

• A lesion identified on a follow-up study in an

anatomical location that was not scanned at

baseline is considered a new lesion and disease

progression.

Response Criteria

New lesions (continued)

It is sometimes reasonable to incorporate the use of

FDG-PET scanning to complement CT in assessment

of progression (particularly possible ‘new’ disease).

New lesions on the basis of FDG-PET imaging can

be identified according to the following algorithm:

Negative FDG-PET at baseline, with a positiveFDG-PET at follow-up is PD based on a new lesion.

No FDG-PET at baseline and a positive FDG-PET at follow-up:• If the positive FDG-PET at follow-up corresponds to

a new site of disease confirmed by CT, this is PD.

• If the positive FDG-PET at follow-up is not con -

firmed as a new site of disease on CT, additional

follow-up CT scans are needed to determine if

there is truly progression occurring at that site

(if so, the date of PD will be the date of the initial

abnormal FDG-PET scan).

• If the positive FDG-PET at follow-up corresponds

to a pre-existing site of disease on CT that is not

progressing on the basis of the anatomic images,

this is not PD.

Time Point Response

Table 1 provides a summary of the overall response

status calculation at each time point for patients

who have measurable disease at baseline.

Table 1. Time point response: Patients withtarget (+/– non-target) disease

Target Non-target New Overalllesions lesions lesions response

CR CR No CR

CR Non-CR /non-PD No PR

CR NE No PR

PR Non-PD /or not No PRall evaluated

SD Non-PD /or not No SDall evaluated

Not all Non-PD No NEevaluated

PD Any Yes or No PD

Any PD Yes or No PD

Any Any Yes PD

CR = Complete ResponsePR = Partial ResponseSD = Stable DiseasePD = Progressive DiseaseNE = Inevaluable

Time Point Response

When patients have non-measurable (therefore non-

target) disease only, Table 2 is to be used.

Table 2. Time point response: Patients withnon-target disease

Non-target New Overalllesions lesions response

CR No CR

Non-CR/non-PD No Non-CR/non-PD1

Not all evaluated No NE

Unequivocal PD Yes or No PD

Any Yes PD

CR = Complete ResponsePD = Progressive DiseaseNE = Inevaluable

1 Non-CR / non-PD is preferred over ‘Stable Disease’ fornon-target disease since SD is increasingly used as anendpoint for assessment of efficacy in some trials. Toassign this category when no lesions can be measured is not advised.

Confirmation

In non-randomized trials where response is the

primary endpoint, confirmation of PR and CR is

required to ensure responses identified are not the

result of measurement error. This will also permit

appropriate interpretation of results in the context of

historical data where response has traditionally

required confirmation in such trials.

However, in all other circumstances, (i.e., in

randomized phase II or III trials or studies where

stable disease or progression are the primary

endpoints), confirmation of response is not required

since it will not add value to the interpretation of

trial results. However, elimination of the requirement

for response confirmation may increase the

importance of central review to protect against bias,

in particular in studies which are not blinded.

In the case of SD, measurements must have met

the SD criteria at least once after study entry at

a minimum interval (in general not less than 6–8

weeks) that is defined in the study protocol.

Missing Assessments andInevaluable Designation

When no imaging/measurement is done at all at a

particular time point, the patient is not evaluable

(NE) at that time point.

If only a subset of lesion measurements are made at

an assessment, usually the case is also considered

NE at that time point, unless a convincing argument

can be made that the contribution of the individual

missing lesion(s) would not change the assigned

time point response. This would most likely happen

in the case of PD.

R ECI ST1.1

Frequently AskedQuestions

*Compiled fromRECIST 1.1 butinclusive of only thoseitems that were notcovered in the mainbody of the article

When measuring thelongest diameter of target lesions in response to treatment, is the same axis that

was used initially used subsequently, even if

there is a shape change to the lesion that

may have produced a new longest diameter?

The longest diameter of the lesion shouldalways be measured even if the actual axis is

different from the one used to measure the lesioninitially (or at a different time point during follow-up). The only exception to this is lymph nodes—perRECIST 1.1 the short axis should always be followedand as in the case of target lesions, the vector ofthe short axis may change on follow-up.

A

Q 1

Are RECIST criteriaaccepted by regulatoryagencies?

Many cooperative groups and members of the pharmaceutical industry were involved

in preparing RECIST 1.0 and have adopted them.The FDA was consulted in their development andsupports its use, though they don’t require it. TheEuropean and Canadian regulatory authorities alsoparticipated and the RECIST criteria are nowintegrated in the European note for guidance for the development of anticancer agents. Manypharmaceutical companies are also using RECISTcriteria. RECIST 1.1 was similarly widely distributedbefore publication.

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Q 2

What if a single non-target lesion cannot bereviewed (for whateverreason)? Does this negate the

overall assessment?

Sometimes the major contribution of a singlenon-target lesion may be in the setting of CR

having otherwise been achieved; failure to examineone non-target in that setting will leave you unableto claim CR. It is also possible that the non-targetlesion has undergone such substantial progressionthat it would override the target disease and renderthe patient PD. However, this is very unlikely,especially if the rest of the measurable disease isstable or responding.

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Q 3

A lesion which was solidat baseline has becomenecrotic in the center. How should this bemeasured?

The longest diameter of the entire lesionshould be followed. Eventually, necrotic lesions

which are responding to treatment decrease in size.In reporting the results of trials, you may wish toreport on this phenomenon if it is seen frequentlysince some agents (e.g., angiogenesis inhibitors)may produce this effect.

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Q 4

If I am going to use MRI to follow disease,what is the minimum size for measurability?

MRI may be substituted for contrast enhancedCT for some sites, but not lung. The minimum

size for measurability is the same as for CT (10 mm)as long as the scans are performed with a slicethickness of 5 mm and no gap. In the event the MRI is performed with thicker slices, the size of a measurable lesion at baseline should be two times the slice thickness. In the event there areinter-slice gaps, this also needs to be considered in determining the size of measurable lesions atbaseline.

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Q 5

Can PET–CT be usedwith RECIST?

At present, the low dose or attenuationcorrection CT portion of a combined PET–CT

is not always of optimal diagnostic CT quality foruse with RECIST measurements. However, if yoursite has documented that the CT performed as partof a PET–CT is of the same diagnostic quality as adiagnostic CT (with IV and oral contrast) then thePET–CT can be used for RECIST measurements.Note, however, that the PET portion of the CTintroduces additional data which may bias aninvestigator if it is not routinely or seriallyperformed.

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Q 6

A patient has a 32%decrease in sum cycle 2,a 28% decrease in cycle 4 and a 33% decrease in cycle 6. Does confirmation of PR have

to take place in sequential scans or is a

case like this confirmed PR?

It is not infrequent that tumor shrinkagehovers around the 30% mark. In this case,

most would consider PR to have been confirmedlooking at this overall case. Had there been two orthree non-PR observations between the two timepoint PR responses, the most conservative approachwould be to consider this case SD.

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Q 7

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